> On Dec 12, 2014, at 7:19 AM, Itamar Heim <ih...@redhat.com> wrote:
> 
> On 12/10/2014 05:47 PM, Jason Greene wrote:
>> Thanks for the suggestions.
>> 
>> Following Maor’s suggestion I was able to add a local domain, but that 
>> required maintenance mode, so I had to failure the engine over to another 
>> host to  make the change to the current host.
>> 
>> I like the appliance solution a little better, although I think it’s best if 
>> I were to run it under its own private KVM process unmanaged by ovirt, so 
>> that its possible to edit and cycle the host. Unfortunately it’s still a bit 
>> cumbersome as you need to have an engine appliance per system or shuffle 
>> around the image with some sort of disaster recovery plan.
>> 
>> I also looked into using gluster or cephfs as a way to share state, but 
>> noticed the BZs about the lack of complete atomicity leading to duplicate 
>> engines.
>> 
>> This is probably not the right place for dev musings, but IMO it would be 
>> great if in a future release there could be a solution that doesn’t require 
>> shared storage, which for smaller use-cases is often too pricey of a 
>> requirement. Ideally, under such a “horizontal” setup, each host could 
>> govern its own management data, and the engine could act more as an 
>> authoritative aggregator, thereby reducing the need for ha (if it fails just 
>> reinstall a clean one and let it reimport everything). It seems like most of 
>> the pieces are already there, with the per host-vdsm instance already 
>> containing much of the data. I’m guessing the missing element is having the 
>> engine support pulling that information as opposed to just pushing it. This 
>> is sort of like a capability that an unnamed proprietary competitor has, so 
>> it might have some sort of appeal. Of course such setups do have 
>> limitations, like you still need shared storage for live migrations and so 
>> on. So I certainly understand
>> the rational behind the existing design. Anyway it’s just some food for 
>> thought.
>> 
> before we go so far out... gluster should work with 3 hosts, we are working 
> on improving the flow for this for 3.6. today it requires quite a few manual 
> steps to do so.
> 

I was looked into that, but I got scared away by:
https://bugzilla.redhat.com/show_bug.cgi?id=1097639

The option I was thinking of trying was drdb to mirror the ovirt appliance 
copied to a block store, and then using something like pacemaker to control 
failover. This would ensure that the engine always follows its data. 

--
Jason T. Greene
WildFly Lead / JBoss EAP Platform Architect
JBoss, a division of Red Hat

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